Type II diabetes is approaching “epidemic” incidence in the United States, driven in large part by a remarkable rise in obesity rates over the past 15 years. According to the American Diabetes Association (ADA), 18.2 million people in the United States, or 6.3% of the population have diabetes. From 1980 through 2003, the number of Americans with diabetes more than doubled (Centers for Disease Control, 2005). Nearly two-thirds of all Americans are now classified as either overweight or obese, a condition that puts them at risk for this kind of diabetes.
The direct medical costs of diabetes and its secondary complications accounted for $160 billion in 2002. The indirect effects of the disease, which include lost workdays, restricted activity days, mortality, and permanent disability, were estimated to be $39.8 billion for the same year. These figures underestimate the effects of diabetes on society, as they do not include the decreased quality of life and resultant pain and suffering that accompany the disease, nor the economic value of unpaid caregivers or the medical expenses of people with undiagnosed diabetes.
The major burden of this disease to the patient and to health care resources is due to the long-term complications that are catastrophic to the eyes, kidneys, nerves, heart and limbs. There is now good evidence that at least the microangiopathy of diabetes is related to the duration and severity of hyperglycaemia. In theory, returning blood glucose levels to normal by replacement insulin injections and other treatments in diabetes should prevent complications, therefore, it is extremely important to monitor blood glucose levels.
Diabetic patients currently measure their won blood glucose by obtaining finger-prick capillary samples and applying the blood to a reagent strip for analysis in a portable meter. Glucose selfmonitoring has had a major impact on improving diabetes care in the last few decades, the disadvantages of this technology include the fact that the discomfort of obtaining a blood sample leads to non-compliance, that testing cannot be performed during sleeping, and that intermittent testing may miss episodes of hyper- and hypo-glycemia. The ideal in-vivo glucose monitoring technology should therefore be non-invasive and continuous.
Billions of dollars of public and private sources have been spent on the research and development of noninvasive or long-term implantable glucose monitoring. However, each of these techniques has significant obstacles and weaknesses. For example, the major problem in measuring glucose concentration in interstitial fluid is that there is a “lag time”. Furthermore, the attachment and measurement in interstitial fluid can also cause skin irritations and rashes. For most implanted or semi-invasive techniques, bio-compatibility is the major problem; even subcutaneously implanted devices with prolonged contact will provoke an inflammatory response.
Prior art techniques direct measurement of blood glucose via either the direct detection of glucose in bodily fluids or indirect measurements via a single physical signal that is dependent on the blood glucose level (e.g., the near infra-red techniques). In general, direct measurement techniques all suffer from problems of invasiveness; indirect techniques suffer from the problem of accuracy.
There is thus a need for a non-invasive and accurate approach for the measurement of blood glucose levels.